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siderable and very long, is directed backwards for its first 
half, then forward for the second. These two parts are 
cemented one against the other, and towards the place 
where the ovaries are, the extremity gives issue to the excita- 
tory organ. The latter very long, slender, and cylindrical in 
a part of its extent, claviform at its extremity, issues forth by 
the anterior genital orifice, probably from the contraction of 
the sheath, which appears to be of a muscular tissue. 
We have to state that this description, differing consider- 
ably from what we find in the works of many authois, is 
taken from M. de Blainville, who had the fortunate opportu- 
nity of dissecting a leech taken in the act of coupling, and in 
which consequently all the parts were in the greatest state of 
development, so that at all events we may rely upon its gene- 
ral truth. This part, however, of the anatomy of this animal 
involves much difficulty. The nervous system of the leech 
is pretty nearly similar to that of the lumbrici, and the rest of 
the class. Placed on the middle abdominal line in the cellu- 
lar tissue, which separates the intestine from the sub-cutane- 
ous muscular stratum, it is composed of a certain number of 
ganglia placed in file, and furnishing, beside the cords of 
communication in front and behind with each other, some 
transverse threads for the external envelope. The number of 
these ganglia appears to be very variable. The first, much 
larger than, and differently composed from, the others, is 
immediately on the under lip. Besides the threads which it 
furnishes to the surrounding parts, there issues forth on each 
side a thick cord, which is continued with a cephalic or epi- 
labial ganglia scarcely thicker than itself, and which gives 
out the nerves of the upper lip. 
Each of the following ganglia is of a lozenge form ; the an- 
terior and posterior angles furnish the double cords winch 
continue the nervous system along the belly , and from the 
